A microphone converts a voice into an electrical signal, and it has becoming smaller. Accordingly, a microphone using micro-electro-mechanical system (MEMS) technology has been developed.
Such a MEMS microphone is more resistant to humidity and heat compared to a conventional electret condenser microphone (ECM), and it may be downsized and integrated with a signal processing circuit.
In general, the MEMS microphone can be classified into a capacitive MEMS microphone and a piezoelectric MEMS microphone.
The capacitive MEMS microphone includes a fixed electrode and a vibration membrane. When an external sound pressure is applied to the vibration membrane, a capacitance value varies because a distance between the fixed electrode and the vibration membrane is changed. The sound pressure is measured based on an electrical signal generated at this time.
The piezoelectric MEMS microphone includes only a vibration membrane. When the vibration membrane deforms by an external sound pressure, an electrical signal is generated due to a piezoelectric effect. The sound pressure is measured based on the electrical signal.
In general, in a case of the capacitive MEMS microphone, a fixed electrode and a vibration membrane are formed using surface micromachining and bulk micromachining. Since the process is complicated and the number of processes increases, it is difficult to manufacture the MEMS microphone. The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention, and therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.